XPS analysis of chitosan–hydroxyapatite biomaterials: from elements to compounds

Abstract

Chitosan (Cs) and hydroxyapatite (Ha) were analysed by X-ray photoelectron spectroscopy (XPS). Phosphorylated Cs microparticles and hybrid Cs/Ha microparticles were prepared and analysed by XPS before and after immersion in a solution 1.5 times more concentrated than a simulated body fluid (SBF). The accuracy of spectrum recording, peak decomposition and peak component assignment was insured by a post-control of charge stabilization, and by the examination of correlations between spectral data guided by stoichiometry and charge balance. The concentration of organic oxygen was determined from the concentrations of the oxidized forms of carbon, allowing a sharper insight into speciation and O 1s peak shape. This indicated that the hydroxide ion of Ha, and hydrogenophosphate if present, give a contribution near 532.4 eV, which overlaps with organic oxygen. As a result of immersion in the 1.5*SBF solution, the formation of CaCO 3 and of Ha material occurred. A quantification could be made for the constituents of biomaterial interest, contaminating salts and paraffin oil residues from the microparticle manufacturing process. The uncertainties regarding the nature of the model calcium phosphate used and the best marker for calcium carbonate were addressed by comparing the possible effect on the output, which was facilitated by using ternary composition diagrams. Whatever their formulation, the native microparticles were found to be coated by a thick layer of paraffin oil. The induction of calcium carbonate and phosphate precipitation or the retention of precipitates by the microparticles was favored by the presence of phosphate in the initial formulation either by phosphorylation or by incorporation of Ha.

Tuning the formation and stability of microcapsules by environmental conditions and chitosan structure

“…Spectral analysis was performed using the XPS Peak software v 4.1. The major N 1s contribution near 399.4 eV was due to non-protonated amine or amide (Nnp); and the higher binding energy side at 401.4 eV could be assigned to protonated amine groups (Npr) [31,32]. 12 The bead grinding method described in our previous study was adopted here with a minor modification [33].…”

The Effect of Different Solvents for Chitosan Solubilization on The Crystal Growth of in situ Prepared Hydroxyapatite

“…Three kinds of peaks can be noticed in pure HA spectrum which were attributed to the adventitious organic contaminants or the adsorption of impurity hydrocarbons during the synthesis procedure. These peaks do not affect the interpretation of our results after CS addition [19,24]. The peak located at 284.6 eV was assigned to the C-C and C-H appeared in all samples and remained almost constant in their areas [24].…”

“…These peaks do not affect the interpretation of our results after CS addition [19,24]. The peak located at 284.6 eV was assigned to the C-C and C-H appeared in all samples and remained almost constant in their areas [24]. However, in all nanocomposite samples, new peak was observed in the range of 286.3 to 288 eV which was related to the chemical bond between carbon and nitrogen or oxygen [C-(N,O)].…”

“…4 (C, D) the peaks at 399.73 and 399.97 ev were assigned to the free amine group (−NH 2 ) which indicated the existence of CS on HA surface. The intensity and the atomic concentration of these peaks increased after dissolving CS in acetic acid (Table 1) indicating that CS was loaded more on the surface of HA [24]. Since the peaks at 399.23 and 399.5 ev are related to the non-protonated amine and the peaks at 401.3 ev is assigned to protonated amine (NH 3 + ).…”

Preparation and blood compatibility of electrospun nanofibrous CTS/PLA mats from chitosan nanopowders and poly(lactic acid)

“…For CL6, There was an N1s peak near 400.0 eV due to the existence of non‐protonated amine or amide (Nnp). And there was a new peak near 285.4 eV which was attributed to CN in the spectrum of CL6, besides those peaks of CO, CO, and CH . The peaks of N1s and CN indicated that NCTS had been successfully blended with PLA in the electrospun nanofibrous mat.…”